In a vehicle, a seatback of a rear seat is typically configured to recline and fold over a seat cushion. By doing so, the space of a luggage compartment of a vehicle may be increased.
Japanese Utility Model Publication No. (Hei.) 3-45634 (see FIG. 1) discloses such a seatback of the rear seat. Specifically, a seatback frame has a first frame with a substantially rectangular panel material. Further, the seatback frame also has a second frame with an annular pipe material, which is adhered to a panel surface of the first frame along its periphery to thereby obtain the required frame rigidity. In addition, the ends of the seatback frame, which are disposed in a lateral direction of the vehicle, are releasably engaged to the panel material of a vehicular compartment side using a locking mechanism.
In a typical rear collision, a crash load is exerted upon the seatback toward a rear of the vehicle due to an inertial force applied by a passenger sitting on the rear seat. In such a case, both the first frame consisting of the panel material and the second frame consisting of the pipe material are bent and become deformed into a bi-planar “<” shape. By doing so, the crash energy can be somewhat absorbed.
However, since the first and second frames are bent locally and deformed at the center portion, the crash energy cannot be effectively absorbed, thereby jeopardizing the safety of the driver and passengers in the vehicle.